An unoccupied space where something may be stored / An unoccupied area or volume. / Vacuum; a space containing nothing at all

Heating of rooms within buildings.

(crystallography, mineralogy) The set of all symmetry operations that can be applied to a given crystal without changing it.

plural of space hopper

The period from the about the time of the launch of Sputnik in 1957 to the present day, during which people ventured into space. / (attributive) Redolent of the space age; appearing futuristic or modern.

That part of an electron tube in which electrons interact with a modulated field

That part of an optical system where real or virtual images are formed

A broad step between flights of a staircase. / (mathematics) Either of the two parts of three-dimensional space divided by a plane.

(mathematics) Any topological space which cannot be written as the disjoint union of two or more nonempty open spaces.

(mathematics) Any Riemann space in which the metric tensors are constants throughout